Types of Chemical Reactions

Five Types of Chemical Reactions

• Remember…a chemical reaction is when one compound is changed into a totally different compound.• While there are millions of different

types of reactions, they can all be classified into five general types.

Five Types of Chemical Reactions

The five types are:1. Synthesis2. Decomposition3. Single Replacement4. Double replacement5. Combustion

Synthesis Reaction

• A synthesis reaction takes place when two or more chemicals react to produce a single chemical.• The reactants can be either elements

or molecules (the product is always a molecule).

A + B AB

Synthesis Reaction

• Actual example:2Na + Cl2 → 2NaCl

Synthesis Reaction

• Practical use – the synthesis of nylon• A key ingredient in toothbrushes,

tents, carpet, clothes, guitar strings…

Decomposition Reaction

• A decomposition reaction takes place when a molecule breaks down into two or more substances.• The reactant is always a molecule

(never a single element).

AB A + B

Decomposition Reaction

• An actual example:H2CO3 → H2O + CO2

Decomposition Reaction

• Practical use – car airbags• The rapid decomposition of sodium

azide causes the bag to inflate with nitrogen gas in about 0.04 seconds!

Single Replacement Reaction

• A single replacement reaction takes place when one element takes the place of another element in a molecule.• The reactant side always consists of

an element and a molecule.

A +BC B + AC

Single Replacement Reaction

• An actual example:2Na + 2H2O → 2NaOH + H2

Double Replacement Reaction

• A double replacement takes place when two molecules exchange elements.• There are at least two molecules on

both sides of the arrow.

AB + CD AD + BC

Double Replacement REaction

• An actual example:CaCO3 + 2HCl → CaCl2 + H2CO3

Combustion Reaction

• A combustion reaction takes place when a hydrocarbon reacts rapidly with oxygen gas.• A hydrocarbon is a molecule made of

carbon and hydrogen atoms.• The products are CO2 and H2O.

CH + O2 CO2 + H2O

Combustion Reaction

• An actual example:CH4 + 2O2 → CO2 + 2H2O

Combustion Reaction• Practical use – internal combustion

engine• Most forms of transportation use this

type of engine.